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Re: [lammps-users] GPU package
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Re: [lammps-users] GPU package


From: Axel Kohlmeyer <akohlmey@...24...>
Date: Mon, 21 May 2018 09:43:51 -0400



On Mon, May 21, 2018 at 9:27 AM, Julian Kerr <julian.kerr@...33....7646...> wrote:
Sorry, my problem was unrelated to compiling. It was resolved by disabling/enabling the GPU. Then, I was able to successfuly run the command
 
mpirun lmp_ubuntu -sf gpu -pk gpu 1 -in in.Li-dendritic.nvt
 
And there were 4 GPU processes by lmp_ubuntu. However, it took 34min, exactly the same as non-GPU run. I understand that GPU-acceleration appears  for large number of atoms, but I expected to withness a tiny contribution. This is the fun part of playing with the variables as mentioned in the manual. If I made a breakthrough I will share it with the community.

​please keep in mind, that you do not have a very powerful GPU with a rather slow memory transfer speed compared to high-end desktop GPUs.
this results in additional overhead. since the GPU kernels essentially have to do twice ​the work (for more efficient parallelization), it is much more challenging to have the GPU acceleration offset the overhead with a moderate sized, mobile GPU compared to a high-end desktop/workstation GPU.
in addition, it depends a lot on the size of the system (as you noted) and the specifics of the force field setup (which you have not provided).

thus i strongly suggest you experiment first with the benchmark examples bundled with LAMMPS before rolling your own. that - and the corresponding performance numbers published on lammps.sandia.gov - will give you an assessment of what acceleration is possible with those inputs and then you can assess what might be possible with your specific setup.

​axel.​

 
Thanks for your excellent support.
 
Sent: Monday, May 21, 2018 at 2:14 PM

From: "Axel Kohlmeyer" <akohlmey@...24...>
To: "Julian Kerr" <julian.kerr@...7646...>
Cc: "LAMMPS Users Mailing List" <lammps-users@...6335.....sourceforge.net>
Subject: Re: [lammps-users] GPU package
 
 
On Mon, May 21, 2018 at 8:44 AM, Julian Kerr <julian.kerr@...7646...> wrote:
Thanks for the clarification, axel and apologies for not providing full information. Makefile.linux looks like
 
ifeq ($(CUDA_HOME),)
CUDA_HOME = /usr/local/cuda-9.1
endif
NVCC = nvcc
# Tesla CUDA
#CUDA_ARCH = -arch=sm_21
# newer CUDA
#CUDA_ARCH = -arch=sm_13
# older CUDA
#CUDA_ARCH = -arch=sm_10 -DCUDA_PRE_THREE
CUDA_ARCH = -arch=sm_30
 
I use CUDA 9.1 on Ubuntu 18.04. The GPU is Quadro K2100M
 
​please also provide the output of lib/gpu/nvc_get_devices
and try to run the example inputs in bench/FERMI on your GPU.
also, please check whether you have the required permissions to access the GPU device.
 
axel.
 
 
 
 
Sent: Sunday, May 20, 2018 at 8:13 PM
From: "Axel Kohlmeyer" <akohlmey@...24...>
To: "Julian Kerr" <julian.kerr@...7646...>
Cc: "LAMMPS Users Mailing List" <lammps-users@...6335.....sourceforge.net>
Subject: Re: [lammps-users] GPU package
 
 
On Sun, May 20, 2018 at 2:51 PM, Julian Kerr <julian.kerr@...7646...> wrote:
I installed the GPU package according to the instruction given at http://lammps.sandia.gov/doc/accelerate_gpu.html
 
Everything went smoothly and when I run the command
 
mpirun lmp_ubuntu -pk gpu 1 -in in.Li-dendritic.nvt
 
the calculaton works well (though I doubt if it is by GPU) but when I run the command
 
​it won't run on the GPU unless you explicitly request pair styles with names ending in /gpu that input
 
 
mpirun lmp_ubuntu -sf gpu -pk gpu 1 -in in.Li-dendritic.nvt
 
​that will try to find /gpu styles, even if they are not explicitly named, by appending /gpu to every style name and falling back to ​non-gpu versions, if gpu variants are not available. please see the LAMMPS manual for more details on this.
 
 
I receive the error:
LAMMPS (16 Mar 2018)
Cuda driver error 999 in call at file 'geryon/nvd_device.h' in line 273.
Cuda driver error 999 in call at file 'geryon/nvd_device.h' in line 273.
Cuda driver error 999 in call at file 'geryon/nvd_device.h' in line 273.
Cuda driver error 999 in call at file 'geryon/nvd_device.h' in line 273.
 
​what kind of GPU do you have? did you compile for CUDA or OpenCL? what version of CUDA - if any - did you use? what are the compiler/GPU settings in your lib/gpu compilation?​
​axel.​
 
 

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--
Dr. Axel Kohlmeyer  akohlmey@...24...  http://goo.gl/1wk0
College of Science & Technology, Temple University, Philadelphia PA, USA
International Centre for Theoretical Physics, Trieste. Italy.

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--
Dr. Axel Kohlmeyer  akohlmey@...24...  http://goo.gl/1wk0
College of Science & Technology, Temple University, Philadelphia PA, USA
International Centre for Theoretical Physics, Trieste. Italy.

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--
Dr. Axel Kohlmeyer  akohlmey@...12...24...  http://goo.gl/1wk0
College of Science & Technology, Temple University, Philadelphia PA, USA
International Centre for Theoretical Physics, Trieste. Italy.